The present invention concerns processing of integrated circuits and pertains particularly to a temperature control carrier head for a chemical mechanical polishing process.
A standard chemical mechanical polishing (CMP) carrier head, such as a ViPPr carrier head available on a Strasbaugh 60DS-SP chemical mechanical polisher, transfers pressure on the back of a wafer to the front of the wafer to control the polish rate as the front of the wafer is being polished. The amount of pressure can increase or decrease the polish rate on the front of the wafer. An increase or decrease in the pressure results in a respective increase or decrease in the polishing rate. Varying the polishing rate across the wafer is done by changing localized back pressure on the wafer.
Heat generated by friction during the polishing process as well as the ambient temperature affects the chemical reaction of slurry used during CMP. If there is too much temperature variation over the surface of the wafer, this can impact uniformity of the polishing performed.
Further, CMP carrier heads use a retainer ring to hold a wafer secure during polishing. The retaining ring exterts pressure on the polishing pad which can change the polishing rate near the edge of the wafer.